Intra-oral 3-d fluorescence imaging

ABSTRACT

Method and apparatus embodiments can generate a volume fluorescence image of a tooth. Method and apparatus embodiments can project structured light patterns onto a tooth and generate a contour (volume) image of the tooth surface from acquired corresponding structured light projection images; then acquire one or more fluorescence images of the tooth generated under blue-UV illumination. A composite image that shows fluorescence image content mapped to the generated contour image can be transmitted, stored, modified and/or displayed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a divisional of U.S. application Ser. No.15/528,773, filed May 23, 2017, which is incorporated herein byreference in its entirety.

FIELD OF THE INVENTION

This invention relates generally to dental imaging and more particularlyto apparatus and methods for providing 3-D contour images that caninclude images from tooth fluorescence.

BACKGROUND OF THE INVENTION

Conventional 2-D imaging has been used, with considerable success, forintra-oral applications. However, because of the particular constraintsand features of the mouth, it is recognized that 2-D imaging has somesignificant limitations for showing tooth structure and cannot providethe level of detail and depth information that would be available with a3-D image, or an image that at least provided reasonable representationof tooth contour.

Fringe projection imaging uses patterned or structured light to obtainsurface contour information for structures of various types. In fringeprojection imaging, a pattern of lines of an interference fringe orgrating is projected toward the surface of an object from a givendirection. The projected pattern from the surface is then viewed fromanother direction as a contour image, taking advantage of triangulationin order to analyze surface information based on the appearance ofcontour lines. Phase shifting, in which the projected pattern isincrementally spatially shifted for obtaining additional measurements atthe new locations, is typically applied as part of fringe projectionimaging, used in order to complete the contour mapping of the surfaceand to increase overall resolution in the contour image.

Fringe projection imaging has been used effectively for surface contourimaging of solid, highly opaque objects and has been used for imagingthe surface contours for some portions of the human body and forobtaining detailed data about skin structure. Teeth present a particularchallenge for contour imaging, due to factors such as relativetranslucency of the tooth and scattering by the tooth material,irregularities in shape and structure, and difficulties in providingsufficient light to surfaces disposed at very different angles.

Structured light imaging techniques more accurately represent toothcontour and overall shape, but do not provide significant informationrelated to the condition of the tooth, such as whether or not caries canbe detected. In response to the need for improved caries detectionmethods, there has been considerable interest in improved imagingtechniques that do not employ x-rays.

A number of methods for showing tooth condition employ fluorescence,wherein teeth are illuminated with high intensity blue, violet, or UVlight and information is obtained from materials in the tooth that areexcited by the illumination energy. This technique, termed quantitativelight-induced fluorescence (QLF) by some researchers, operates on theprinciple that sound, healthy tooth enamel yields a higher intensity offluorescence under excitation from some wavelengths than doesde-mineralized enamel that has been damaged by caries infection. Thecorrelation between mineral loss and loss of fluorescence for blue lightexcitation is then used to identify and assess carious areas of thetooth. A different relationship has been found for red light excitation,a region of the spectrum for which bacterial by-products in cariousregions absorb and fluoresce more pronouncedly than do healthy areas.

While fluorescence can provide useful information on tooth condition,fluorescent images themselves are 2-D images. It can be appreciated thatthere would be value in presenting fluorescence image results along withat least some amount of contour information about the tooth.

SUMMARY OF THE INVENTION

An aspect of this application is to advance the art of medical imaging,particularly for dental intra-oral imaging applications.

Another aspect of this application is to address, in whole or in part,at least the foregoing and other deficiencies in the related art.

It is another aspect of this application to provide, in whole or inpart, at least the advantages described herein.

It is an object of the present invention to advance the art ofintra-oral imaging, particularly with respect to processing andpresentation of fluorescence image content. Embodiments of the presentinvention combine features of both contour imaging and fluorescenceimaging in order to provide enhanced information about the condition ofa patient's teeth and mouth.

An advantage offered by apparatus and/or method embodiments of theapplication relates to generating a three dimensional representations ofteeth and/or gums including fluorescence information.

An advantage offered by apparatus and/or method embodiments of theapplication relates to projecting a structured light pattern onto thetooth and acquiring a plurality of fluorescence projection images of thetooth and/or generating a contour image of a tooth surface from anacquired plurality of fluorescence projection images.

These objects are given only by way of illustrative example, and suchobjects may be exemplary of one or more embodiments of the invention.Other desirable objectives and advantages inherently achieved by thedisclosed invention may occur or become apparent to those skilled in theart. The invention is defined by the appended claims.

According to an aspect of the application, there is provided a methodfor obtaining an image of a tooth executed at least in part by acomputer processor that can include projecting a structured lightpattern onto the tooth and acquiring a plurality of structured lightprojection images of the tooth; generating a contour image of the toothsurface from the acquired plurality of structured light projectionimages; acquiring one or more fluorescence images of the tooth generatedunder blue-UV illumination; and displaying a composite image that showsfluorescence image content mapped to the generated contour image.

According to an aspect of the application, there is provided a methodfor obtaining an image of a tooth executed at least in part by acomputer processor that can include projecting a structured lightpattern onto the tooth and acquiring a plurality of fluorescenceprojection images of the tooth; generating a contour image of the toothsurface from the acquired plurality of fluorescence projection images;and displaying the generated contour image.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The foregoing and other objects, features, and advantages of theinvention will be apparent from the following more particulardescription of the embodiments of the invention, as illustrated in theaccompanying drawings. The elements of the drawings are not necessarilyto scale relative to each other.

FIG. 1 is a schematic diagram that shows components of an exemplaryintra-oral imaging apparatus embodiment according to the application.

FIG. 2A is a schematic diagram showing exemplary optical components ofan intra-oral imaging camera embodiment according to the application.

FIG. 2B is a schematic diagram showing another exemplary opticalarrangement that uses only a single broadband light source in anintra-oral imaging camera embodiment according to the application.

FIG. 2C is a schematic diagram showing another exemplary opticalarrangement of an intra-oral imaging camera embodiment in which a fringepattern generator is in the illumination path for internal light sourcesaccording to the application.

FIG. 2C is a schematic diagram showing a camera in which a fringepattern generator is in the illumination path for internal lightsources.

FIG. 3 is a plan view showing a structured light pattern used forcontour imaging according to selected embodiments of the application.

FIG. 4 is an image showing an exemplary structured light patternprojected onto a model of a tooth.

FIG. 5 is a logic flow diagram that shows an exemplary method embodimentfor providing fluorescence imaging data correlated with the surfacecontour of teeth and other oral features according to the application.

FIG. 6 is a perspective view that shows an exemplary contour imageincluding fluorescence image content according to embodiments of theapplication.

FIG. 7A is a schematic diagram that shows the activity of fluorescedgreen light for caries detection.

FIG. 7B is an image that shows a demineralization lesion conditiondetected in a 2D fluorescence image.

FIG. 8A is a schematic diagram that shows the behavior of fluoresced redlight for caries detection.

FIG. 8B is a 2D fluorescence image that shows incipient caries detectedaccording to red fluorescence.

FIG. 9 is a logic flow diagram that shows an exemplary method embodimentfor generating and displaying a contour image formed from fluorescenceimage content according to the application.

FIG. 10 is a logic flow diagram that shows an exemplary methodembodiment for displaying a contour image along with lesion informationaccording to the application.

FIG. 11 shows an operator interface for viewing exemplary contour imagesand mapped data according to certain embodiments of the application.

FIG. 12 shows exemplary indexing of a composite image using a displayeddental chart according to certain embodiments of the application.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

The following is a description of exemplary embodiments, reference beingmade to the drawings in which the same reference numerals identify thesame elements of structure in each of the several figures.

In the drawings and text that follow, like components are designatedwith like reference numerals, and similar descriptions concerningcomponents and arrangement or interaction of components alreadydescribed are omitted. Where they are used, the terms “first”, “second”,and so on, do not necessarily denote any ordinal or priority relation,but are simply used to more clearly distinguish one element fromanother.

In the context of the application, the term “optics” is used generallyto refer to lenses and other refractive, diffractive, and reflectivecomponents used for shaping and directing a light beam.

In the context of the application, the terms “viewer”, “operator”, and“user” are considered to be equivalent and refer to the viewingpractitioner, technician, or other person who views and manipulates animage, such as a dental image, on a display monitor. An “operatorinstruction” or “viewer instruction” is obtained from explicit commandsentered by the viewer, such as by clicking a button on a camera or byusing a computer mouse or by touch screen or keyboard entry. Theoperator instruction can initiate acquisition and processing of a singleimage or acquisition and processing of a number of different image typesneeded for generating a composite image, including patterned andflat-field images, from broadband visible and near-UV or blue-UVsources. To help reduce motion artifacts, composite image generationuses a sequence of images acquired within as short a time span aspossible, such as immediately following each other in close succession,for example. It is understood that some finite amount of time isrequired in order for detector 52 to acquire light and to provide imagedata for each obtained images. Where multiple images are required, theycan be obtained in any order and used to generate a composite image.According to an embodiment of the application, generating the compositeimage occurs only after it is determined that the plurality ofstructured light projection images and the one or more fluorescenceimages have been acquired from the same camera position.

The term “highlighting” for a displayed feature has its conventionalmeaning as is understood to those skilled in the information and imagedisplay arts. In general, highlighting uses some form of localizeddisplay enhancement to attract the attention of the viewer. Highlightinga portion of an image, such as an individual tooth or a set of teeth orother structure(s) can be achieved in any of a number of ways,including, but not limited to, annotating, displaying a nearby oroverlaying symbol, outlining or tracing, display in a different color orat a markedly different intensity or gray scale value than other imageor information content, blinking or animation of a portion of a display,or display at higher sharpness or contrast.

An image is displayed according to image data that can be acquired by acamera or other device, wherein the image data represents the image asan ordered arrangement of pixels. Image content may be displayeddirectly from acquired image data or may be further processed, such asto combine image data from different sources or to highlight variousfeatures of tooth anatomy represented by the image data, for example. Asused in the context of the application, the terms “image” and “imagedata” are generally synonymous, with the understanding that these termsrelate to either the digital data representation or the physicaldisplayed representation according to context.

The term “at least one of” is used to mean that one or more of thelisted items can be selected. The term “about” indicates that the valuelisted can be somewhat altered, within some reasonable tolerance, aslong as the alteration does not result in nonconformance of the processor structure to the illustrated embodiment. The term “exemplary”indicates that a particular description or instance is used by way ofexample, rather than implying that it is an ideal.

The term “set”, as used herein, refers to a non-empty set, as theconcept of a collection of elements or members of a set is widelyunderstood in elementary mathematics. The term “subset”, unlessotherwise explicitly stated, is used herein to refer to a non-emptyproper subset, that is, to a subset of the larger set, having one ormore members. For a set S, a subset may comprise the complete set S. A“proper subset” of set S, however, is strictly contained in set S andexcludes at least one member of set S.

As used herein, the term “energizable” relates to a device or set ofcomponents that perform an indicated function upon receiving power and,optionally, upon receiving an enabling signal.

The term “actuable” has its conventional meaning, relating to a deviceor component that is capable of effecting an action in response to astimulus, such as in response to an electrical signal, for example.

The phrase “in signal communication” as used in the applicationindicates an electrical connection by which two or more devices and/orcomponents are capable of sharing a signal or signals that travel oversome type of signal path. Signal communication may be wired or wireless.The signals may be communication, power, data, or energy signals thatmay communicate information, power, and/or energy from a first deviceand/or component to a second device and/or component along a signal pathbetween the first device and/or component and second device and/orcomponent. The signal paths may include physical, electrical, magnetic,electromagnetic, optical, wired, and/or wireless connections between thefirst device and/or component and second device and/or component. Thesignal paths may also include additional devices and/or componentsbetween the first device and/or component and second device and/orcomponent.

Embodiments of the application address the need for improved intra-oralimaging by using combinations of reflectance and fluorescence imagingtechniques, along with contour imaging from patterned-light images andmapping of flat-field images to a detected contour structure. Varioustypes of images can be acquired, processed, and displayed, enabling moredetailed analysis and assessment of tooth and mouth features to assistin patient diagnosis.

FIG. 1 is a schematic diagram that shows components of an exemplaryintra-oral imaging apparatus embodiment. As shown in FIG. 1, anintra-oral imaging apparatus 10 can obtain images of a tooth 20. Anintra-oral camera 30 is in signal communication with a control logicprocessor 40, also termed a computer processor in the application.Signal communication is provided over a cable 32 or, alternately, over awireless connection (not shown). Processor 40 is in signal communicationwith a display 42 and an operator interface 44, such as a keyboard forcommand entry and a mouse or other pointer device. It can be appreciatedthat processor 40 can be embodied in a number of different ways, withcomputer processing circuitry internal and/or external to camera 30. Incertain exemplary method and/or apparatus embodiments, processor 40 iscapable of providing (e.g., with camera 30), onto the illumination path,in close succession and/or during temporally adjacent time periods,flat-field light or patterned illumination from either the visible orblue-UV light sources, in response to an operator instruction.

FIG. 2A is a schematic diagram showing exemplary optical components ofan intra-oral imaging camera embodiment according to the application.FIG. 2A shows optical paths for imaging components of one embodiment ofintra-oral camera 30 in more detail. Control logic processor 40 may beexternal to camera 30, as shown in FIG. 1, or may be internal to camera30. Alternately, processor 40 may use a distributed logic processingarrangement, so that some processing functions are performed withincamera 30 and other functions performed by one or more additionalprocessors that acquire data from camera 30. A fringe pattern generator50 takes light energy from one or more illumination sources, such as abroadband visible or white light source 66 and a second light source 68for excitation energy that is generally at shorter wavelengths, such asan ultraviolet (UV) or near-ultraviolet or blue source, referred to as a“blue-ultraviolet” or “blue-UV” source in subsequent description. For UVillumination, the emitted light from excitation source 68 is generallybelow about 410 nm. For blue-UV illumination, the excitation source 68emits light typically within the range between about 350 nm-500 nm. Anadvantageous portion of this blue-UV illumination range that isgenerally effective for exciting visible fluorescence centersapproximately about 405 nm. A light combiner 60, such as a beam splitterwith a dichroic surface, directs the illumination to the fringe patterngenerator 50. Fringe pattern generator 50 may be a spatial lightmodulator, for example, that is energizable to form one or more patternsof light from light sources 66 and 68 or to form a flat field of lightthat does not have a pattern for general reflectance or fluorescenceimaging. Among types of spatial light modulator that can be used forgenerating patterned light are digital micromirror arrays, such as theDigital Light Processor from Texas Instruments, Inc., Dallas Tex.; andliquid crystal device (LCD) arrays. Fringe pattern generator 50 can beof a transmissive type (as shown in FIG. 2A) or a reflective type thatmodulates incident light by reflection (not shown).

A broadband light source 56 provides flat-field white light illuminationfor reflectance images. A blue-UV source 58 provides flat-field blue-UVillumination for fluorescence imaging. Either or both light sources 56and 58 can be light emitting diodes (LEDs). Each of the threeillumination paths shown in dashed lines and the imaging path to thedetector include various optics 54, represented by a lens symbol in FIG.2A and including lenses, filters, polarizers/analyzers, path-foldingoptics, apertures, or other components that help to condition and directthe illumination or imaging light appropriately.

Optionally, motion of camera 30 can be determined between images. Forexample, an optional motion detector 38 or the like can be used to sensemotion of camera 30 between images. This information can be used to helpcorrelate image content, both for relating structured light images toeach other and for relating fluorescence images to reflectance imagecontent. Alternately, motion can be detected by image analysis softwareroutines executed by control logic processor 40. An optional modeselection switch 78 provides settings that allow operator selection ofan imaging mode for intra-oral camera. Switch 78 can allow the selectionof a reflectance image capture, fluorescence image capture, or contourimage capture using fluorescence or reflectance images and/orcombinations thereof. Processor 40 is capable of switching rapidlybetween the different light sources so that the different types ofimages can be acquired from the same camera 30 position in closesuccession, as quickly as detector 52 can process and provide image dataoutput. For any two images taken adjacently, one immediately after theother, image capture is considered to be “in close succession” when theinterval between adjacent image acquisitions is determined, more thanany other single factor, by the response time required by the system forforming and recording the image data, including component refresh time,for example.

FIG. 2B is a schematic diagram showing another exemplary opticalarrangement in an intra-oral imaging camera embodiment according to theapplication. FIG. 2B shows a camera 30 embodiment similar to that ofFIG. 2A but not using combiner 60, so that only a single light source 67is used for contour imaging. In this configuration, fringe patterngenerator 50 uses light energy from one light source 67, including, butnot limited to a broadband visible or white light or blue-UV source.Flat-field illumination for reflectance or fluorescence imaging isprovided from light sources 56 or 58 respectively.

FIG. 2C is a schematic diagram showing another exemplary opticalarrangement in an intra-oral imaging camera embodiment according to theapplication. FIG. 2C shows camera 30 embodiment in which fringe patterngenerator 50 is in the illumination path for the light sources (e.g.,all) within camera 30. Patterned illumination or a flat field ofillumination, whether for reflectance or fluorescence imaging or contourimaging, can be formed by a spatial light modulator controlled byprocessor 40. Spatial light modulators include liquid-crystal devices,or micro-mirror or micro-electromechanical systems (MEMS) devices, forexample. An optional motion detector 38 is also included as part ofcamera 30.

An optional flat field reflectance image can be useful for detecting andshowing shade differences between ceramic or other restorations in twoor more different restoration areas.

FIG. 3 shows an exemplary structured light pattern 62 that can begenerated from fringe pattern generator 50. In this example, structuredlight pattern 62 is a pattern of parallel lines 84, such as thatconventionally used for fringe projection imaging, using techniquesfamiliar to those skilled in the contour imaging arts. More elaboratelight patterns can be generated; however, the use of one or morepatterns of parallel lines has been shown to be effective in determiningsurface contour. FIG. 4 shows, on a model tooth structure, how oneexemplary structured light pattern 62 can appear on acquired images ofteeth.

FIG. 5 is a logic flow diagram that shows an exemplary method embodimentfor providing fluorescence imaging data correlated with surface contourof teeth and/or other oral features according to the application. Thelogic flow diagram of FIG. 5 shows steps in exemplary processembodiments that can combine fluorescence image content with structuredata obtained from contour imaging. In an acquire structured lightimages step S100, the structured light pattern is projected andcorresponding images captured and used for generating surface contourinformation in a contour image generation step S110. More than onestructured light pattern may be projected and imaged for a more completecharacterization of surface contour at that imaging perspective. Anacquire fluorescence images step S120 can also be executed at or nearthe same time as step S100. Acquire fluorescence images step S120directs higher-energy blue-UV illumination to the tooth surface andobtains flat-field fluorescence images that can then be mapped to thecontour image in a mapping step S130. Fluorescence images, eithercontour or flat-field images, can be obtained in video mode. Camera 30is held in the same position for acquiring contour images andfluorescence images in close succession, with the acquisition speedgated only by the response time required by detector 52 (FIGS. 2A-2C).Following mapping step S130, an optional image processing and analysisstep S140 can be performed to aid in caries detection for bacteriaactivity and demineralization. In addition to caries detection, stepS140 can also apply other clinical diagnostics, such as aided detectionof tetracyclines. Tetracyclines are known to absorb light in the 320-400nm UV range. UV excitation from about 358 to 364 nm is particularlyeffective in allowing detection of nanogram-level quantities of thesecompounds. Step S130 is optional where only this tetracycline detectionfunction is needed; processing would proceed from step S120 to stepS140. Such a resulting image, showing fluorescence image data mapped tothe surface contour, is displayed in a display step S150.

It should be noted that imaging steps shown in the FIG. 5 sequence canbe executed in any order. Position tracking of camera 30, either usingimaging techniques or some other type of position-sensing mechanism,helps to provide the needed correlation between the structured lightimages and the correlation of the contour image that is generated tofluorescence image data.

Contour image generation from two or more structured light images isknown to those skilled in the image processing arts. Contour imagegeneration may use triangulation, camera location or movementcompensation, and image analysis in order to obtain surface informationfrom the obtained images.

Mapping step S130 can be executed in a number of ways. According to anembodiment of the application, the fluorescent image is obtained withcamera 30 in the same position that is used for obtaining the structuredlight images. Thus, the same imaging perspective applies for one or morestructured light images and one or more corresponding fluorescent imageor images. Structured light images and fluorescence image can beobtained in this manner for a number of imaging perspectives, asdetermined by different camera movements or positions. Then, at eachimaging perspective, the same image coordinates can serve for bothreconstruction of the contour image and mapping of the fluorescencecontent to the contour image. FIG. 6 shows, in schematic form, mappingof the fluorescence content to the reconstructed contour image. As analternative to camera position sensing, mapping processes that utilizeimage analysis methods can be used. These methods, well known to thoseskilled in the image processing arts, analyze imaged structures anddetect similar features in the obtained images in order to correlate theimages to each other.

The fluorescence image content can be analyzed for various conditions.For example, a correlation between mineral loss and loss of fluorescencefor blue light excitation can be used to identify and assess cariousareas of the tooth. A different relationship has been found for blue orred light excitation regions of the spectrum within which bacterialby-products in carious regions absorb and fluoresce more pronouncedlythan do healthy areas.

Applicants note some references related to optical detection of caries.

U.S. Pat. No. 4,515,476 (Ingmar) describes the use of a laser forproviding excitation energy that generates fluorescence at some otherwavelength for locating carious areas.

U.S. Pat. No. 6,231,338 (de Josselin de Jong et al.) describes animaging apparatus for identifying dental caries using fluorescencedetection.

U.S. Patent Application Publication No. 2004/0240716 (de Josselin deJong et al.) describes methods for improved image analysis for imagesobtained from fluorescing tissue.

U.S. Pat. No. 4,479,499 (Alfano) describes a method for usingtransillumination to detect caries based on the translucent propertiesof tooth structure.

U.S. Patent Application Publication No. 2004/0202356 (Stookey et al.)describes mathematical processing of spectral changes in fluorescence inorder to detect caries in different stages with improved accuracy.Acknowledging the difficulty of early detection when using spectralfluorescence measurements, the '2356 Stookey et al. disclosure describesapproaches for enhancing the spectral values obtained, effecting atransformation of the spectral data that is adapted to the spectralresponse of the camera that obtains the fluorescence image.

In commonly-assigned U.S. Pat. No. 7,668,355 entitled “Method forDetection of Caries” by Wong et al., a method and apparatus that employsboth the reflectance and fluorescence images of the tooth is used todetect caries. This method takes advantage of the observedback-scattering, or reflectance, for incipient caries and in combinationwith fluorescence effects, to provide a dental imaging technique todetect caries.

Certain exemplary apparatus and/or method embodiments of the presentinvention can utilize fluorescence response in at least two different,overlapping or non-overlapping spectral bands. For example, FIG. 7Ashows information that is provided from fluorescence in the greenspectral band. Excitation light 70 of blue and near UV wavelengths(nominally centered near about 405 nm according to an embodiment of theapplication) is directed toward tooth 20 with an outer enamel layer 22and inner dentine 24. Fluoresced light 72 of green wavelengths,approximately in the range from 500-550 nm, is detected from portions ofthe tooth 20 having normal mineral content, not exhibiting perceptibledamage from decay. In the representation shown in FIG. 7A, ademineralized area 26 is more opaque than healthy enamel and tends toblock the incident excitation light 70 as well as to blockback-scattered fluorescent light from surrounding enamel. This effect isused by the FIRE method described in commonly assigned U.S. Pat. No.7,596,253 entitled “Method and Apparatus for Detection of Caries” toWong et al., wherein the fluorescence green channel data in a 2D stillimage is combined with reflectance image data in a 2D still image toheighten the contrast of caries regions.

FIG. 7B is a 2D image that shows an early caries condition detected oftooth 20 using the FIRE method. An area 28, circled in FIG. 7B, showssuspected caries with demineralization.

The fluoresced red light has different significance, for example,indicating the presence of bacterial metabolic products. Bacteria thattypically cause a caries lesion, plaque, or tartar typically generateby-products that fluoresce in the red spectrum, above about 600 nm. FIG.8A shows the behavior of fluoresced red light 53 for caries detection.Here, a caries lesion 55 has significant bacterial activity, evidencedby emission of perceptible amounts of fluoresced light 53 in the redspectral region in response to excitation light 70. With properfiltering of the fluorescent light, this red wavelength emissionindicates an active lesion 46, as circled in FIG. 8B.

FIG. 6 is a perspective view that shows an exemplary contour image thatcan include fluorescence image content (e.g., mapped) according tocertain embodiments of the application. FIG. 6 can show an exampleoutput of display step S150 (FIG. 5), a composite image 80 with a cariesarea 76 displayed on a contour image 74. The displayed composite image80 may include one or more areas of bacterial activity, highlightedaccording to relative severity or type of bacterial activity that issensed, such as caries, for example.

According to an alternate apparatus and/or method embodiments of theapplication, intra-oral imaging apparatus 10 can be used to obtain,process, and display contour images obtained using fluorescence ratherthan using reflected light. FIG. 9 is a logic flow diagram that shows anexemplary method embodiment for generating and displaying a contourimage formed from at least fluorescence image content according to theapplication. An acquire structured light images step S200 illuminatesthe tooth or other oral feature with structured light that is intendedto excite fluorescence, such as UV or near-UV light. The structuredlight pattern may be the conventional parallel lines arrangement shownwith respect to FIGS. 3 and 4 or may have a different characteristicpattern. Fluoresced light resulting from this illumination pattern isthen captured in a set of multiple images, for each of a number ofimaging perspectives, in similar manner to that used for reflectanceimaging. A contour image can then be formed in a contour imagegeneration step S210. Areas of bacterial activity can be detected fromthe fluorescent light, as noted previously; this process is performed inan optional identify bacterial areas step S220. A display step S230 canthen display the contour image with areas showing bacterial activityhighlighted.

It should be noted that imaging steps shown in the FIG. 9 sequence canbe executed in any order and can also be executed continuously fordynamic updating. Position tracking of camera 30, either using imagingtechniques or some other type of position-sensing mechanism, helps toprovide the needed correlation between the structured light images andthe correlation of the contour image that is generated to fluorescenceimage data.

FIG. 10 is a logic flow diagram that shows an exemplary methodembodiment for displaying a contour image along with lesion informationin surrounding soft tissue according to the application. FIG. 10 shows asequence for using a combination of reflectance contour imaging andfluorescence imaging to detect and display areas of lesion insurrounding tissue of the patient's mouth. In an acquire structuredlight images step S300, a pattern of structured light is projected ontothe teeth and tissue two or more times at each of two or more spatiallyshifted positions to obtain a number of structured light projectionimages. With camera 30 held at the same position for capture of thepatterned light images, a contour image that includes the surroundingtissue can then be formed in a contour image generation step S310. Anacquire fluorescence image step S320 then executes, in whichfluorescence image content can be obtained from tissue that is near thetooth for which contour information has been obtained. The light forexciting fluorescence can be flat-field light, such as light in the UVor near-UV wavelength range, as described previously. Maintaining camera30 in the same position allows registration of the fluorescence andcontour information. Various sensors (represented as motion detector 38in FIGS. 2A-2C) can be used to detect inadvertent camera 30 movement;image processing can also be used to determine whether or not camera 30is in the same position for acquiring the needed images. According to anembodiment of the application, processing for subsequent steps S330 andS340 does not proceed until contour and fluorescence images that can besuitably registered to each other are obtained.

In an identify lesion areas step S330 in the FIG. 10 sequence, imageanalysis is used to identify tissue areas indicative of lesions. Adisplay step S340 then correlates the imaged tissue locations withimaged teeth and displays identified lesion areas in a composite image.Highlighting of the lesion can be provided for the image displayed as aresult of the FIG. 10 sequence.

The sequence shown in FIG. 10 can be used, for example, to aid indetection of mucosal lesions. Lesion detection can use spectralanalysis, for example, to identify a suspect area of tissue. It has beenobserved that excitation of oral mucosa using UV in the range from about375-440 nm generates fluorescence response from epithelial keratins.Abnormal tissue has reduced fluorescence intensity, indicative ofvarious types of lesions.

It should be noted that image acquisition steps shown in the FIG. 10sequence can be executed synchronously or in a different orderarrangement from that shown, with different image content andcorresponding processing updated as new images are acquired. Positiontracking of camera 30, either using imaging techniques or some othertype of position-sensing mechanism, helps to provide the neededcorrelation between the structured light images and the correlation ofthe contour image that is generated to fluorescence image data.

The processed image content can be presented to the viewer in any of anumber of ways. FIG. 11 shows an exemplary operator interface screen ondisplay 42 that allows the viewer to enable or disable display of imagecontent within composite image 80, such as viewing the caries area 76along with, or separate from, contour image 74, or viewing only contourimage 74. This same type of operator interface arrangement can be usedfor enabling or disabling views of lesions. Pan and zoom imagemanipulation functions are also available from the operator interface.

Embodiments of the application also allow imaged tooth content to bestored in conjunction with dental chart information. FIG. 12 shows anexemplary dental chart 88 on display 42, with composite image 80contents indexed to a particular tooth 20 according to tooth placement.

In one embodiment, a method for obtaining an image of a tooth caninclude projecting a structured light pattern onto the tooth andacquiring a plurality of structured light projection images of thetooth; generating a contour image of the tooth surface from the acquiredplurality of structured light projection images; acquiring one or morefluorescence images of the tooth generated under blue-UV illumination;generating a composite image having fluorescence image content mapped tothe generated contour image according to detected camera movement;identifying one or more restoration areas in the mapped fluorescenceimage content; and displaying the generated composite image with the oneor more identified restoration areas highlighted.

In one embodiment, a method for forming an intra-oral image can includeprojecting a structured light pattern onto one or more teeth andacquiring a plurality of structured light projection images of theteeth; generating a contour image of the tooth surface from the acquiredplurality of structured light projection images; acquiring one or morefluorescence images of the one or more teeth generated under blue-UVillumination; generating a composite image having fluorescence imagecontent for the teeth mapped to the generated contour image; identifyingone or more areas of the teeth indicative of tetracycline materialsaccording to the mapped fluorescence image content; and displaying thegenerated composite image with the one or more identified areasindicative of tetracycline materials highlighted.

In one embodiment, a method for obtaining an intra-oral image caninclude projecting a structured light pattern onto one or more teeth andat least some portion of the surrounding tissue and acquiring aplurality of structured light projection images of the teeth andsurrounding tissue; generating a contour image of the tooth andsurrounding tissue surface from the acquired plurality of structuredlight projection images; acquiring one or more fluorescence images oftissue near the tooth generated under blue-UV illumination; generating acomposite image having fluorescence image content for the tissue mappedto the generated contour image; identifying one or more areas indicativeof tissue abnormality in the mapped fluorescence image content; anddisplaying the generated composite image with the one or more identifiedtissue abnormality areas highlighted.

In one embodiment, an apparatus for intra-oral imaging can include afirst broadband visible light source for providing flat-fieldillumination for reflectance imaging; a blue-UV light source forproviding flat-field illumination for fluorescence imaging; a secondbroadband visible or blue-UV light source for generating a patternedillumination; a fringe pattern generator in the illumination path andenergizable to form a projection pattern of light from the second lightsource for projection onto one or more teeth; a control processor thatis energizable to detect when the amount of apparatus motion is below athreshold and to switch between light sources in close succession forobtaining images according to the patterned and flat-field illumination;and a detector in the path of light from the tooth and energizable toform an image according to light in the illumination path.

Consistent with one embodiment, the control logic processor 40 of thepresent invention is a type of computer processor that utilizes acomputer program with stored instructions that perform on image datathat has been stored and accessed from an electronic memory. As can beappreciated by those skilled in the image processing arts, a computerprogram of an embodiment of the present invention can be utilized by asuitable, general-purpose computer system, such as a personal computeror workstation or by a microprocessor device contained within intra-oralcamera 30 (FIG. 1). However, many other types of computer systems can beused to execute the computer program of the present invention, includingnetworked processors. The computer program for performing the method ofthe present invention may be stored in a computer readable storagemedium. This medium may comprise, for example; magnetic storage mediasuch as a magnetic disk such as a hard drive or removable device ormagnetic tape; optical storage media such as an optical disc, opticaltape, or machine readable bar code; solid state electronic storagedevices such as random access memory (RAM), or read only memory (ROM);or any other physical device or medium employed to store a computerprogram. The computer program for performing the method of the presentinvention may also be stored on computer readable storage medium that isconnected to the image processor by way of the internet or othercommunication medium. Those skilled in the art will readily recognizethat the equivalent of such a computer program product may also beconstructed in hardware.

It should be noted that the term “memory”, equivalent to“computer-accessible memory” in the context of the application, canrefer to any type of temporary or more enduring data storage workspaceused for storing and operating upon image data and accessible to acomputer system, including a database, for example. The memory could benon-volatile, using, for example, a long-term storage medium such asmagnetic or optical storage. Alternately, the memory could be of a morevolatile nature, using an electronic circuit, such as random-accessmemory (RAM) that is used as a temporary buffer or workspace by amicroprocessor or other control logic processor device. Displaying animage requires memory storage. Display data, for example, is typicallystored in a temporary storage buffer that is directly associated with adisplay device and is periodically refreshed as needed in order toprovide displayed data. This temporary storage buffer can also beconsidered to be a memory, as the term is used in the application.Memory is also used as the data workspace for executing and storingintermediate and final results of calculations and other processing.Computer-accessible memory can be volatile, non-volatile, or a hybridcombination of volatile and non-volatile types.

Exemplary embodiments according to the application can include variousfeatures described herein (individually or in combination).

While the invention has been illustrated with respect to one or moreimplementations, alterations and/or modifications can be made to theillustrated examples without departing from the spirit and scope of theappended claims. In addition, while a particular feature of theinvention can have been disclosed with respect to one of severalimplementations, such feature can be combined with one or more otherfeatures of the other implementations as can be desired and advantageousfor any given or particular function. The term “at least one of” is usedto mean one or more of the listed items can be selected. The term“about” indicates that the value listed can be somewhat altered, as longas the alteration does not result in nonconformance of the process orstructure to the illustrated embodiment. Finally, “exemplary” indicatesthe description is used as an example, rather than implying that it isan ideal. Other embodiments of the invention will be apparent to thoseskilled in the art from consideration of the specification and practiceof the invention disclosed herein. It is intended that the specificationand examples be considered as exemplary only, with a true scope andspirit of the invention being indicated by the following claims, and allchanges that come within the meaning and range of equivalents thereofare intended to be embraced therein.

That which is claimed:
 1. An apparatus for intra-oral imagingcomprising: a broadband visible light source; a blue-UV light source; alight combiner that is disposed to combine both visible and blue-UVlight onto a single illumination path; a fringe pattern generator in theillumination path and configured to project a pattern of light onto atooth; a control processor configured to operate with the light combinerto provide, onto the illumination path, flat-field or patterned lightfrom the visible or blue-UV light source; and a detector in the path oflight reflected from the tooth, wherein the detector is configured toacquire one or more structured light projection images of the tooth fromflat-field light projected with the visible light source and to acquireone or more fluorescence images of the tooth from flat-field lightprojected with the blue-UV light source, according to light in theillumination path; wherein the control processor is configured to:generate a contour image of a surface of the tooth from the acquired oneor more structured light projection images; generate a composite imagehaving fluorescence image content for the tooth mapped to the generatedcontour image; identify one or more areas of the tooth indicative oftetracycline materials based at least in part on the mapped fluorescenceimage content; and cause display, via a display device, of the generatedcomposite image that shows fluorescence image content mapped to thegenerated contour image and with the one or more identified areas ofindicative of tetracycline materials emphasized.
 2. The apparatus ofclaim 1, where the light combiner has a dichroic surface, where thefringe pattern generator is a spatial light modulator or a liquidcrystal device array, further comprising: a motion detector in signalcommunication with the control processor; and a mode selection switch toselect the broadband or blue-UV light sources and to select the fringepattern generator.
 3. The apparatus of claim 1, comprising: a secondbroadband visible or blue-UV light source for generating a patternedillumination, where the fringe pattern generator is energizable to forma projection pattern of light from the second light source forprojection onto the tooth, and where the control processor detects whenan amount of apparatus motion is below a threshold to switch betweenlight sources in close succession for obtaining images according to thepatterned and flat-field illumination.
 4. The apparatus of claim 1further comprising a motion detector that is in signal communicationwith the control processor.
 5. An apparatus for intra-oral imagingcomprising: a broadband visible light source; a blue-UV light source; alight combiner that is disposed to combine both visible and blue-UVlight onto a single illumination path; a fringe pattern generator in theillumination path and configured to project a pattern of light onto atooth; a control processor configured to operate with the light combinerto provide, onto the illumination path, flat-field or patterned lightfrom the visible or blue-UV light source; and a detector in the path oflight reflected from the tooth, wherein the detector is configured to:acquire one or more structured light projection images of the tooth fromlight projected with the visible light source, wherein the one or morestructured light projection images also reflect from other teeth andtissue surrounding the tooth; and acquire one or more fluorescenceimages of the tooth from flat-field light projected with the blue-UVlight source, wherein the acquired fluorescence images include tissuenear the tooth; wherein the control processor is configured to: generatea contour image of a surface of the tooth from the acquired one or morestructured light projection images, wherein the generated contour imageis of the tooth and surrounding tissue surface from the acquired one ormore structured light projection images; generate a composite imagehaving fluorescence image content for the tissue mapped to the generatedcontour image; identify one or more areas indicative of tissueabnormality in the mapped fluorescence image content; and cause display,via a display device, of the generated composite image that showsfluorescence image content mapped to the generated contour image andwith the one or more identified areas of tissue abnormality emphasized.6. The apparatus of claim 5, where the light combiner has a dichroicsurface, where the fringe pattern generator is a spatial light modulatoror a liquid crystal device array, further comprising: a motion detectorin signal communication with the control processor; and a mode selectionswitch to select the broadband or blue-UV light sources and to selectthe fringe pattern generator.
 7. The apparatus of claim 5, comprising: asecond broadband visible or blue-UV light source for generating apatterned illumination, where the fringe pattern generator isenergizable to form a projection pattern of light from the second lightsource for projection onto the tooth, and where the control processordetects when an amount of apparatus motion is below a threshold toswitch between light sources in close succession for obtaining imagesaccording to the patterned and flat-field illumination.
 8. The apparatusof claim 5 further comprising a motion detector that is in signalcommunication with the control processor.
 9. The apparatus of claim 5,wherein the composite image is a three-dimensional fluorescence image.10. The apparatus of claim 5, wherein the control processor is furtherconfigured to generate both flat-field and structured light projectionimages using blue-UV illumination.
 11. The apparatus of claim 5, whereinthe control processor is further configured to generate both flat-fieldimage and one or more structured light projection images using visiblelight illumination.
 12. The apparatus of claim 5, wherein causingdisplay of the generated composite image further comprises emphasizingone or more areas of bacterial activity.
 13. The apparatus of claim 5,wherein acquiring one or more fluorescence images is performed in avideo imaging mode.
 14. The apparatus of claim 5, wherein the controlprocessor is further configured to store contents of the composite imageindexed to a displayable dental chart.
 15. The apparatus of claim 5,wherein the control processor is further configured to change thedisplayed image to disable the fluorescence image content.
 16. Theapparatus of claim 5, wherein the control processor is furtherconfigured to: generate the composite image having fluorescence imagecontent mapped to the generated contour image according to detectedcamera movement; identify one or more restoration areas in the mappedfluorescence image content; and display the generated composite imagewith the one or more identified restoration areas highlighted.
 17. Theapparatus of claim 5, wherein the control processor is furtherconfigured to: generate the composite image having fluorescence imagecontent mapped to the generated contour image according to detectedcamera movement; identify one or more restoration areas in the mappedfluorescence image content; and display the generated composite imagewith the one or more identified restoration areas highlighted.